Abstract: A trailer security apparatus is mounted to the frame of a trailer to prevent an unauthorized usage of the trailer. The trailer security apparatus has a switch that is selectively moveable between an unlocked position and a locked position. The trailer security apparatus also has a lock device responsive to the switch to clearingly disengage from wheels on the trailer to permit rolling the trailer in the unlocked position of the switch, and to interferingly engage one or more of the wheels on the trailer to prevent rolling the trailer in the locked position of the switch.